Level XInclude support in parsers?

Seeing the recent post on XInclude...

What is the level of support of XInclude in XML processors?

I don't see it as required by the baseline XML spec, but does current 
circumstances mean that you would de-facto expect an XML parser to support 
it?

What is the support like in common tools such as Xerces, .NET, Java and 
libxml2 etc?

Thanks,

Pete.
--
=============================================
Pete Cordell
Tech-Know-Ware Ltd
for XML Schema to C++ data binding visit
 http://www.tech-know-ware.com/lmx/
 http://www.codalogic.com/lmx/
=============================================